Thermal control device for storage batteries



- Dec. 2, 1947. J. H. LITTLE ETAL I I 2,431,945

THERMAL CONTROLDEVICE FOR STORAGE BATTERIES Fiied Nov. 2, 1943 PIGULA703 AND CUT-OUT PELAY INVENTORS Jam! h! 1772: AIID BY W/u/AM 1 FAD) MEIRATTORNEYS Patented Dec. 2, 1947 THERMAL CONTROL DEVICE FOR STORAGEBATTERIES John H. Little, Huntington W'oods, Mich, and William J. Rady,Anderson, Ind, assignors to General Motors Corporation, Detroit, Miclm,a

corporation of Delaware Application November 2, 1943, Serial No. 508,694

4 Claims;

This invention relates to battery charging systems and its aim is toprotect the battery from excessive decomposition of the water in theelectrolyte, particularly when the battery is substantially fullycharged and warm. This arm is accomplished by providing means controlledby battery temperature and charging generator voltage for increasing theresistance of the charging cirwit to reduce the amount of currentflowing to the battery. A resistance element in the charging circuit isnormally by-passed by a relay whose magnet coil is controlled by athermal switch in the battery and by a second relay whose magnet coil isconnected with the generator terminals.

A further aim of the present invention is to provide a battery that isespecially designed so that it is feasible to assemble the thermalswitch from the exterior of the battery and below the normal level ofthe electrolyte and still not have the switch come in contact with theelectrolyte, but also protect it from fumes caused by a too high ratecharge, with the result that the corrosive liquid and fumes are excludedfrom the metal parts of the switch. l

Still another aim of the invention is the provision of a specialenclosure for the thermal switch, which enclosure has 'a heat conductingwall immersed in a controlling electrolyte so as to effect a uniformoperation of the thermal switch irrespective of the electrolyte leveldeviation from the normal level. This is, accomplished by providing thebattery case with a recess adapted to receive a cup-shaped cover withthe thermal switch mounted thereon, said cup-shaped cover being fittedwith the recess when the cover is inverted and positioned within therecess, said cover forming double thickness walls within the walls ofthe recess so that the only single thick ness wall is the bottom Wall ofthe recess.

Further objects and advantages of the present invention will be apparentfrom the followin description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the invention isclearlyshown.

In the drawings:

Fig. 1 is a wiring diagram of battery charging system embodying thepresent invention.

Fig. 2 is a longitudinal sectional view of a thermal switch located inabattery cell cover.

Fig. 3 is a view of the thermal switch looking in the direction of arrow3 of Fig. 2.

Referring to Figs. 2 and 3, a bat'terycell cover it) provides a hollowmember I l depending from the cover. This member comprises a skirtclosed by a wall l2 and which constitutes a recess or well l3 forhousing a thermal switch M. The bottom wall which closes the skirtdepends a substantial distance below the cover Ill so that it will beimmersed in the electrolyte. The normal level of electrolyte in the cellis indicated by the line l5. The thermal switch M, as shown in thedrawing, comp-rises a cup-shaped case or cap l6 having a stud or post Hto which one end of a spiral bimetal element [8 is attached. The elementIt carries a contact 9 for engaging a contact 20, mounted on an ear 2'!of a bracket 22 adjustable in an arcuate slot 23, concentric with thecenter of the stud IT. The bracket 22 has an arcuate slot 24 forreceiving a screw 25, threaded into an insert 26 in the case iii. Thescrew 25, when threaded home in the insert 2'6, holds the bracket in theposition necessary to provide a certain initial gap between the contactsl9 and 29. The length of the gap will determine the degree oftemperature to which the battery will attain when the contacts close.When this gap is greater, the temperature will be higher and vice versa.The thermal switch is readily affected by changes in battery celltemperature.

The thermal switch, including the cup-shaped case of insulatingmaterial, has the same outside diameter as the recess l3 so that the rimwill fit snugly with the internal surfaces of the recess performing asubstantial hermetic seal therewith.

In the present instance, the case includes an annular rim or flange 3!],the ends of which, rest upon the bottom wall l2. In this arrangement,the flange 3i! and the skirt ll form a double thickness wallwith theresult that fumes which surround the case I'll, while in use, aresubstantially eliminated from the metal parts within the case I 5. Itwill be noted, that the lowermost edges of the spiral bimetal strip 18are adjacent the bottom wall I 2, which is a single thickness Wall so asto effect a uniform operation of the thermostatic switch irrespective ofthe electrolyte level deviation from the normal level indicated by theline l5.

At the time of forming the cap, it is formed with suitable apertures toreceive the reduced end of the post I! and the insert 26 and the recess23 to receive the bracket 22. The post I! and insert 26 protrude throughthe wall as shown in Fig. 2 to make provisions for external connectionswith insulated conductors 32 and 33 respectively. The externalconnections are covered with an insulating material 34. The cap isfitted into the recess and is maintained in sealed or fluid tightrelation by additional insulating material 35 applied over the top ofthe material 34. It is to be understood, the material could be apreformed plate with suitable apertures through which the conductors 32and 33 are threaded.

With a thermostatic switch so constructed as sealed as hereinabove setforth, which is shown in Fig. 2. it will be appreciated that thethermostatic switch is enclosed within a chamber 31 that is completelyisolated from electrolyte, fumes and other outside foreign matter whichmay cause corrosion of the metal elements of the thermostatic switch.Due to the character of the assembly, the thermostatic switch l4, theswitch is positioned adjacent the one thickness wall 12 which isnormally immersed in the electrolyte so that irrespective of thedeviations in the electrolyte level, the operation of thermostaticswitch I4 is uniform, in that the heat passing through the wall l2 intothe chamber 31 is somewhat localized in raising the temperature withinthe chamber.

In accordance with the present invention, provision is made for thecontrol of current to the battery by heat generated in the battery. Thisis illustrated diagrammatically in Fig. 1. As shown, a generator 40, isconnected through a voltage regulator and cutout relay unit M, anammeter 42 and a resistance 43 with a battery 44, a cell of whichcarries the thermal switch M. The contacts 45 and 46 of a relay 4'!normally shunt the resistance 43 as indicated by the heavy linesconnecting the generator 40 and battery 44. The magnet coil 48 of relay4! is energized by current from the generator 40 when contacts [9 and 20of thermal switch I4 are engaged concurrently with the engagement ofnormally open contacts 49 and 50 of a relay whose magnet coil 52 isconnected across the generator armature 53.

When the battery 44 is substantially fully charged, the generatorvoltage is sufficient to cause an armature 55 of the relay 5| to movedown to close contacts 49 and 50. This alone will not cause the magnetcoil 48 of relay 4! to be energized. If when the contacts 49 and 50 ofrelay 5| are closed, the contacts [9 and 20 of thermal switch l4 closedue to an elevated battery temperature, so if when the contacts l9 and20 of switch 14 are closed, the contacts 49 and 50 of relay 5| close dueto an elevated generator voltage, the magnet winding 48 of relay 4'! isenergized to pull the relay armature 60 down to separate contacts 45, 46thereby interrupting the shunt circuit of resistance 43 and renderingsaid resistance effective, as indicated by heavy broken lines in Fig. 1,to decrease the flow of current to the battery 44 to protect it fromoverheating.

The load of lamps Si or other current consuming devices connected withammeter 42 by switch 62 is not affected by the reduction in batterycharging current.

While the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. A thermal control device for use in combination with a storagebattery case comprising, a thermostatic switch; a battery cover made ofmolded insulating material and including a thermostat-receiving recessintegrally molded therewith to provide a bottom wall of a certainthickness and so positioned and dimensioned as to be at least partiallyimmersed in electrolyte when electrolyte is within the case, saidthermostatic switch being positioned within the recess so as to beresponsive to temperature changes surrounding the walls of said recess,and means for hermetically sealing said thermostatic switch within saidrecess and providing side walls which are substantially thicker than thethickness of the bottom wall whereby accurate temperature control of theelectrolyte is obtained.

2. A thermal control device for use in combination with a storagebattery case comprising a battery cover made of molded insulatingmaterial for closing the case and including a receiving recessintegrally molded therewith as to be at least partially immersed inelectrolyte when electrolyte is within the case; a cup-shaped cap; athermostatic switch mounted within the cap, said cap having a press fitwithin the recess when the cap is inverted and positioned thereinperforming a substantially hermetic seal therewith, said cap formingdouble thickness walls within the recess so that only a single thicknesswall is the bottom wall of the recess whereby accurate temperaturecontrol of the electrolyte is obtained.

3. A thermal control device for use with a storage battery case havingcells containing electrolyte comprising, a closure for the case made ofmolding insulating material and including a rigid, close ended tubularshell depending from the closure with the closed end arranged to extendbelow the normal level of the electrolyte; a cover for the shell; athermostatic switch supported by the cover, said cover having an annularflange to provide a press fit within the shell and positioning thethermostatic switch within the shell and adjacent the closed end of theshell, said annular flange forming a double side wall above the bottomwall whereby temperature control of the electrolyte is obtained. saidthermostatic switch having external cable connections with metallicelements of the switch which protrude through the cover; and sealingmeans disposed about the external connections and also having sealingengagement with the closure, said sealing means operating to excludecorrosive fumes from the external connections and from the metallicelement of the switch within the shell.

4. A thermal control device for use in combination with a storagebattery case containing electrolyte comprising, a battery closure forclosing the case made of non-corrosive insulating material and includinga casing extending downwardly from the closure and having a closed lowerend, said casing having a thin wall section adapted to be immersed inthe electrolyte; a thermal switch adapted to control a circuit andpositioned within the casing and responsive to temperature changes ofthe electrolyte; a cap to close the casing to form a chamber andincluding depending portions to fit within the casing to form doublethickness side walls except around the thin Wall portion so that whenthe electrolyte is heated the heat will be substantially localizedthrough 5 the thin wall portion as it passes into the chamber andthereby provide a more uniform operation of the switch.

JOHN H. LITTLE. WILLIAM J. RADY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 418,701 Dey Jan. 7, 18901,478,084 Whittington Dec. 18, 1923 1,602,559 Strawrnyer Oct. 12, 19262,377,596 Williams June 5, 1945 Number 6 Name Date Callender Feb. 9,1943 Kopf July 7, 1942 Beetem July 12, 1932 Ogden Sept. 26, 1922Leingang Feb. 23, 1932 Cheeseman Apr. 5, 1932 Richards Feb. 16, 1943Andres Sept. 2, 1919 Schmidt Nov. 22, 1910 Creighton June 11, 1912Strawmyer et a1. June 5, 1923 Nelson Aug. 24, 1926 Nelson Oct. 28, 1930Adams Jan. 26, 1937

